Rockburst，collapse，large deformation of shotcrete layers after support，rock cracks and other damage phenomena appeared in the underground caverns of Jinping I，Houziyan and other large hydropower projects during construction. Systematic researches have seldom been performed on the deformation and instability modes of surrounding rock and the controlling measures. Based on the collected geological and design data，the geophysical surveying，the monitored data and the field investigation in underground caverns of Dagangshan，1st stage of Jinping，Houziyan，Guandi and other typical hydropower projects during construction，the failures of surrounding rock are divided into 3 modes：the rock structure controlled and gravity-driven mode；the stress-driven mode and the mixed mode according the controlling factors. The failure modes can also be divided into 16 basic modes according to the main project sites where instability occurs in 5 areas of the caverns. The proposed controlling measures were used in Houziyan project to show their feasibility and effectiveness.

Frequency analysis of blast vibration is one of the important foundations for developing the control technology of blast vibration damage. Based on the spectrum expression of vibration with a damping term for the spherical charge in tough rock mass and LS-DYNA numerical simulations，the attenuation of dominant frequency and average frequency of blast vibration were analyzed. The attenuation of dominant frequency and average frequency of blast vibration induced by cylindrical charge were studied with the numerical simulations. The results show that for both the spherical or cylindrical charges，the dominant frequency of blast vibration does not attenuate strictly with the increasing of distance to the blast site. Both the multimodal structures of vibration spectrum and the difference of decay rate between the high-frequency and the low-frequency contribute to the mutation or fluctuation at some distance during the frequency attenuation. The average frequency has the pattern of regular attenuation. Theoretical analysis results were validated by the empirical data gotten from engineering.

Deformation and fracture of brittle marble is closely related to the extension of internal microcracks，and the macroscopic mechanical response of marble depends on its mesoscopic structures. Because the micro cracks are sealed in rock bodies，it is very difficult to grasp the development mechanism of the internal microcracks. With the help of the three-dimensional theory of particle flow and introducing the BPM model and the technology of super unit clump，a mesoscopic structure model of marble in terms of the mineral configurations was established on the basis of the testing result of SEM on the mineral contents of marble from the underground powerhouse of Jinping I hydropower station. The mesoscopic mechanical parameters of marble based on the sensitivity analysis was determined according to the indoor testing results of the uniaxial and triaxial compression and the mesoscopic numerical model of marble was also constructed. The deformation and fracture and the expansion process of marble under different stress states and stress paths were analyzed through numerical simulations. The numerical results of the macroscopic mechanical response of marble were found to agree well with the laboratory testing results. The numbers of microcracks grew slowly initially and soon exponentially under the condition of uniaxial and low confining pressures，however，the growth curve was approximately an “S” shape under the condition of high confining pressure. As the increasing of the confining pressure，the proportion of the tensile cracks reduced gradually，and the shear cracks increased. Under the identical initial confining pressure，the axial strain at the peak strength of rock was smaller and the proportion of tensile cracks was higher in the unloading stress path than the ones in the loading stress path. The tensile cracks played the leading role in the unloading process and eventually caused the tensile macro fracture surface to be formed，indicated that the volume expansion effect of marble under unloading was more significant and the brittle characteristics was more obvious. Under the different stress states and stress paths，the control mechanism of tensile crack propagation interacted with the one of shear crack friction，one grew slowly，the other grew fast.

A novel nonlinear shear-slipping model(named as biexponential model) as well as the load transfer solutions was firstly developed for predicting the full-range interfacial behavior of the tensile anchor. The features of the load transfer and the load-displacement curve during the full-range process of pullout were studied in detail. The measured results from the laboratory and in-situ experiments were used to verify the load transfer solutions and the above predicted features of the tensile anchor. The biexponential model was found to describe reasonably the nonlinear and softening behavior of the anchoring interface of tensile anchor. The axial forces and displacements calculated from the load transfer solutions agree well with the measured values. During the full-range pullout process，the load transfer in the fixed segment of the tensile anchor exhibits a loading and a sliding stage. During the loading stage，the shear stress distribution evolves from a monotone decaying curve with the maximum value at the pull end into a single peak curve，and then further evolves into the other monotone decay curve with the maximum value at the far end during the sliding stage. The load-displacement curve is a single peak curve and the peak is approximately flat when the anchorage length is large.

Due to the good integrity，homogeneity and low porosity and permeability of Beishan granite，Beishan has been considered as a candidate for high-level radioactive waste repository. In this study，triaxial compression tests with the measurements of permeability were performed on granite samples using the gas pulse transient technique. Based on the observations of the initiation and propagation of microcracks in the granite samples and the characteristics of the strain-deviatoric stress curves，the permeability variation of the granite samples with the deviatoric stress was analyzed with a micromechanical model. The initial permeability of the Beishan granite at zero deviatoric stress state is in the magnitude of 10－19 m2. The permeability decreases in the initial region of microcrack closure，keeps constant in the elastic region，increase stably and then dramatically the following the unstable regions of crack growth. The closure of preexisting microcracks in the initial loading stage leads to a reduction of permeability of one order in magnitude. The permeability at the failure state increases 2–3 orders of magnitude. The increase of confining pressure from 5 MPa to 10 MPa induces a permeability decrease of one order in magnitude. The numerical simulated results with the micromechanical model are in good agreements with the experimental data，which verifies that the mechanical and hydraulic properties of the granite on the macroscopic scale are essentially governed by the alterations of the microstructural features and the crack connectivity. The permeability variation of the granite samples is consistent with the growth of damage density，in which weak anisotropy of the permeability is the result of the damage growth pattern. The results achieved in this study are useful for assessment of the excavation-induced damage zone，the permeability variation and the long-term performance of the high-level radioactive waste repository systems.

In order to understand the spatial distribution of stress tensors of initial geostress field and to identify its relationship with the cavern group arrangement for hydropower plant site in high geostress region of deep valley，a new method and an operation procedure for obtaining a quantitative and fine numerical initial geostress field based on the coupling of 3D initial geostress calculation model and the structural calculation model containing excavation details were proposed considering the evolution process of river valley，using the space analysis method of stress tensor and the multi-core parallel computing technique. Then，the initial geostress field distribution at Jinping I hydropower station was identified with the method and verified against the field phenomenon of deformation and failure. The underground cavern groups of Jinping I hydropower station were  found to be in the stress transitional region near the deep valley with the high geostress levels and the large stress variations and the high initial geostress environment was thus formed. The average principal stress ratio is about 1.9–2.5 and the rock strength-stress ratio is about 1.5–3.0 in this transitional region. Under the high initial 3D geostress，the low strength-stress ratio and the high principal stress ratio，the deformation and the failure and the depth of unloading relaxation of the surrounding rock during the construction of the underground powerhouse cavern groups were found to be larger than the ones of the cavern groups of the same size in other projects. The locations and distributions of the stress induced deformation and failure confirm the reasonability of the initial 3D geostress field obtained and also verify that the above proposed quantitative model of geostress field is correct and feasible. On this basis，a method of layout design for the underground powerhouse cavern groups located in high geostress area was proposed，considering the three-dimensional geostress，the strength to stress ratio and the structure characteristic，etc. The proposed design method reflects the load characteristics of caverns，the structure characteristics and the bearing capacity of surrounding rock. Using the above design method，some principles and procedures are put forward from a qualitative point of view，which includs how to determine the location of the main cavern，the longitudinal axis，the cavern spacing and type，etc.

During the entire failure process，high arch dam as a statically indeterminate rock structure breaks  locally at first；then the whole system enters the nonlinear deformation stage；and finally the overall structure failure happens. Consequently，it is difficult to evaluate the global stability of a high arch dam using a single criterion. In this paper，the entire failure process was analysed adopting the overload method to study the stability of high arch dams. Meanwhile，3 safety factors(K1，K2，K3) based on the geological model test and the norm criterion of the curve of plastic complementary energy were discussed and compared. 3 safety factors(K–1，K–2，K–3) to simulate the failure process were proposed in this paper by using the theory of deformation reinforcement. The relationships between K1，K2，K3 and K–1，K–2，K–3 were discussed through analysing the results of model tests and the numerical computations completed in recent years. Results indicate that high consistency exists between two criteria and two criteria can validate each other.

Due to the terrain and the complicate geological conditions，the underground powerhouse near the abutment often affects the safety and stability of dam-foundation of super high arch dam. The interaction of dam and underground powerhouse at Wudongde dam was analyzed considering the influences of the distance，the angle and the strength of rock mass. 3D nonlinear finite element analysis with Drucker-Prager yield criterion was carried out. The displacements，the stress，the arch thrust and the overall safety factors of dam and powerhouse foundation of different analysis cases were obtained for analyzing the interaction of dam and underground powerhouse. The results show that the deformation of the abutment is larger when the powerhouse is close to the dam. The dam-powerhouse interaction has little influence on the overall stability of the dam-foundation system.

The caving zones of two layered coal seams within a short distance after the coal mining overlap so that the disturbed zone caused by tunnel construction under the area of the double-deck mined-out seams is larger than the case of single mined out seam；which affects the supporting structure of the tunnel and the stability of surrounding rocks. Indoor tests of similarity model to simulate the tunnel construction was carried out and the ground movements of the mined-out area and the internal forces of the initial supporting structure were measured with the displacement meters，the earth pressure cells and the embedded electric resistance strain gauges. The test results demonstrate that the settlements of mined-out area mainly occur during the second stage of the tunnel excavation，i.e. the excavation of the upper section of the tunnel and the closing of the initial support. The smaller the dip angles of seams are，the larger the settlement rate. The steeper the settlement curve，the slower the convergence speed in the later period and the bigger the settlement value. The supporting structure of the tunnel carries a certain amount of eccentric loads in the inclined double-deck mined-out area，and the bigger the dip angle，the more pronounce the eccentric load. The maximum earth pressure mainly occurs in the invert arch. The anchoring effect of rock bolt is poor due to the mined-out area loosens. The maximum bending moment of the steel arch appears at arch heel and the axial force closed to the mined-out area is quite low which is not beneficial to the stability of the support structure. With the increasing of the dip angle of the mined-out area，the scope of positive bending moment of vault is closer to the coal mined-out area. The maximum bending moment and the eccentric distance increase notably while the stability of the supporting structure decreases.

The different effects of applying the steel frame and the steel grid frame in high geostress region were investigated during the construction of Daliang tunnel in LXS–7 of Lanzhou—Xinjiang double line Railway. The experimental sections applying the section steel and the steel grid are 20 meters in length each. Numerical simulations were carried out. The settlement of the tunnel crown and the arch foot，the horizontal convergence，the surrounding rock pressure and the stress of initial supporting steel framework were compared through experiments and numerical simulation. The section with the steel frame had the settlement and the horizontal convergence controlled more effectively than the one with the steel grid. But the contact pressure of surrounding rock and steel reached 336 kPa，much higher than the cases of the section with steel grid support. In the section of steel grid，the settlement of tunnel crown reached 350 mm after a week，with the rapid displacement increasing. To control the deformation of the surrounding rock，multiple support including the steel grid and the steel frame were set up. The settlement of tunnel crown reached a stable value of 446 mm and the surrounding rock pressure reached 190 kPa. The deformation of surrounding rocks and the stress of initial supporting steel frameworks were finally effectively controlled，so as to indicate that the multiple support is an effective measure of controlling the large deformation of surrounding rocks.

The engineering geological characteristics of the surrounding rock of large hydropower caverns in high    geostress areas are very different from those in the normal geostress area. So the rock classification and evaluation system should be different. However，the hydropower classification(HC) method of rock mass for evaluating the rocks in high geostress areas has still many defects，and has caused some deviations between the evaluated results and the real situations. The purpose of this paper is to correct and optimize the HC method in high geostress areas. Firstly，the problems existed in the HC method were analyzed comprehensively，and some appropriate amendments were proposed. Secondly，some new proposals for ground stress evaluation and classification criteria were proposed through extensive collecting and collating of the information of high geostress of the current large-scale hydropower projects. Then，the evaluation ideas and methods of HC for high geostress areas were optimized systematically and the corresponding methods of optimization were proposed. Finally，the plant of Houziyan hydropower station under construction was analyzed，and the comparative analysis was made to confirm the suitability of this optimization method.

The topographical and geological condition of dam area of Dagangshan hydropower station is complex and the bank slope is steep.  The well developed geological structures，unloading fissures，high earthquake intensity and complicated slope structures lead to the problem of stability of the high slope at the right bank. The potential sliding mode of the slope was studied in detail considering the site conditions of geology and construction. A synthetic scheme of reinforcing treatment was thus proposed and used for the belt with dense unloading fissures at the right bank slope. The stability analysis of slope was carried out with different numerical methods. The results indicate that the safety factor of the slope after the reinforcement meets the requirement of the control standard. At the same time，the data of in-situ monitoring indicate that the slope is stable and the scheme of reinforcing treatment is reasonable and effective.

During“5•12”Wenchuan earthquake，the strong ground motion caused Erguxi tunnel #1 to deform and crack. Under the influences of the aftershocks，the precipitation and the impounding of reservoir etc，the creep rate of the slope gradually increases resulting large deformation of slope and squeezing the Erguxi tunnel #1 to be damaged severely. 3D laser scanning technology was used to obtain the surface image of the tunnels and the tunnel deformation was calculated with the acquired optical results. The maximum extrusion was found to be 1.08 m. The finite element software ANSYS was used to back analyze the structural loads. The element discretization of the lining structure was achieved through the load-structure discrete method with a spring to represent the constraint of rock. Repeated iterations were carried out to get the structural load of the slope on the deep lining to be around：F = 16 807–23 737 kN. A suitable treatment program for the tunnel was put forward based on the value of the load on the structure.

The surrounding rock mass of the underground caverns at Houziyan hydropower station is under high ground stresses and has a low strength-to-stress ratio，leading to severe rock deformations and failures in the process of construction. The deformation and fracture characteristics of the surrounding rock mass were analyzed according to the geological conditions，the data from monitoring and geophysical detection，and the construction process. The proportions of the measured points with the displacements greater than 50 mm in three main caverns are 17.2%，27.3% and 9.4% respectively. The deformations of the surrounding rock mass of the underground caverns are much greater than the ones of the underground caverns at other stations in the same period. The largest displacement is in the rock of category III1，which indicates that the deformation of rebound of the relatively complete and hard rock due to unloading under high ground stress are quite large. The depths of surrounding rock deformation reache 5 to 15 m，even up to 23 m. The deformation of surrounding rock was found to be closely related to the excavation with a stepped process of development. The deformation of the surrounding rock is largely stress driven with the stress redistribution playing the dominant role and the one to be gravity driven controlled by the adverse combination of structural planes played less roles.

A platform for construction information collecting was established using the internet of things. The real-time dynamic data transmission to and from the inside and the outside of underground cavern group was achieved. A calculation method of the damage reduction of surrounding rock during construction was proposed to provide the dynamic warning indicator of surrounding rock at any construction state based on the method of strength reduction and numerical simulations. A method of real-time comprehensive evaluation and early warning  using the mixed composition operators was proposed based on the observed behavior. If an alert occurs，the best route for evacuation will be provided by the system and sent to the PDA for everyone in the underground cavern group. Finally，a real-time method of safety evaluation and early warning system for large-scale underground cavern group were developed based on a mixed programming technology with Python and VB.net. The system realizes the dynamic early warning and emergency directing during construction，providing safety guarantee for engineering and lives.

The failure patterns and deformation characteristics of surrounding rock masses in underground powerhouse caverns with different ratios of rock strength to in-situ stress(RSS) were analyzed and summarized，and the relationships between the RSS and the bearing capacity，the failure patterns and the deformation characteristics of surrounding rock masses were expounded. Based on the large amount of the statistical design data concerning the layout of caverns in hydropower stations，an innovative design method for the layout of underground caverns was proposes. The specific quantitative indicators and the related calculation formulas were presented. This method emphasized the important influence of RSS on the layout of caverns and based on the past experiences，the numerical analysis results and the recent findings in this field. The proposed method also took account into the interactions of adjacent caverns，the characteristics of in-situ stress in canyon region where caverns located，the classification of in-situ stress according to its magnitude and the distribution of weak discontinuities(e.g. joints and faults which are the main factors affecting the stability of underground caverns) etc.. It can be applied to the layout design of underground caverns under various stress levels or complex geological conditions.

The reservoir bank collapse is a common geological problem in the reservoir impounding process. There often exists significant difference between the prediction and the actual collapse ranges. A new method，named as balanced alluvial accumulation approach，is proposed for the prediction of reservoir bank collapse on the basis of the surveying of bank collapse cases of more than 10 large reservoirs in China，the measurement on all kinds of stable angle of collapse phenomenon，and the analysis of the applicable conditions，the collapse mechanism and the collapse  factors of the current prediction method of bank collapse. The new method has the reasonable initial points and prediction parameters and overcomes the deficiency of the traditional prediction method of bank collapse. It is also verified by a case study.

The typical geomorphic features of high mountains and deep canyons and the regional high geostress conditions lead to the engineering complexity and the difficulty of construction of the large-scale underground cavern groups for hydropower stations beyond the scope of present knowledge. Utilizing the massive monitored data from the safety monitoring with the scale in ever expansion，an analysis and evaluation system of the rapid monitoring of large-scale underground caverns in the Southwest China was established by means of the monitoring softwares. The evaluation of the stability of surrounding rock of caverns and the design of the construction process of cavern group of the underground powerhouse can be carried out with the system，so as to ensure the stability of surrounding rock and the safety operation of the underground caverns. Through the statistical analysis of a large number of monitored data，five displacement evaluation indices and five supporting load evaluation indices were proposed to monitor the stability of surrounding rock in the system. Relating the grading of evaluation indices for the grading of surrounding rock stability，the stability evaluation of the surrounding rock in underground caverns can be obtained rapidly. The evaluation system was applied to the subsequent construction of caverns and was proved appropriate.

A new method was proposed for three-dimensional analysis of the bearing capacity of shallow rectangular footing based on the modification of normal stresses over the slip surface. Firstly，the shape of the slip surface was assumed as an ellipsoid composed of a set of log-spirals with different initial radii in the direction of the longer axis of the footing base. Secondly，a method for calculating the bearing capacity of a fixed three-dimensional slip surface was established based on the modification of normal stresses over the slip surface to improve the limit equilibrium solution of 3D slope stability. Finally，the bearing capacities were obtained for the footing with selected fixed three-dimensional slip surfaces resulted from changing the positions of the pole of log-spirals so that the minimum bearing capacity was determined. The bearing capacity coefficients were then given for calculating the bearing capacity with the method of superposition in the conventional bearing capacity formula. The effects of the angle of internal friction and the length-width ratio of footing were investigated. An example was presented to calculate the bearing capacity and the calculated results were compared with those from other methods. The results demonstrate its accuracy，reasonability and high effectiveness in the three-dimensional bearing capacity analysis of rectangular shallow footing.

When the soils around the foundation pit are actually in an unsaturated state，the design of anti-overturning  retaining wall based on the saturated soil mechanics neglecting matric suction is unreasonable. Assuming the matric suction with the uniform and linear distributions，equations for critical embedment depths of anti-overturning were obtained on the basis of the unified solution of shear strength for unsaturated soils under the plane strain condition，and the moment equality considering the intermediate principal stress effect and the strength nonlinearity. The procedure of engineering application with the obtained results was given and the parametric analysis about the coefficient of critical embedment for anti-overturning was discussed. The proposed results are orderly solution series. The effect of strength theory on the anti-overturning design for rigid retaining wall of foundation pit led to remarkable difference. The greater strength of unsaturated soils in comparing to the saturated soil could be utilized considering the intermediate principal stress effect. The critical embedment coefficient was significantly influenced by the matric suction and its distributions. Therefore，the distributions of matric suction should be reasonably assumed and some engineering measures should be adopted to ensure its stability. Two methods can deal with the effect of strength nonlinearity of unsaturated soils：the method 1 with a small stable suction angle which is simple but conservative；while the method 2 with piecewise hyperbolic suction angle is precise but slightly complicated. The dual effects of high matric suction on the strength of unsaturated soil and the structural design should be correctly understood.

Groundwater level in coastal region fluctuates periodically due to wave or tides. The response of the pore pressures of the ground near the retaining wall is vital for pit excavation. In this study，a single layer ground with finite thickness around the pit to be excavated was considered to be isotropic and homogeneous. The fluctuating water level at the boundary was assumed to be a sinusoidal function. The seepage area around the pit was divided into three zones. Assuming the total stresses of soil keeping constant，the two-dimensional consolidation equations were decoupled. A semi-analytical solution of pore pressure of the ground around the pit with gravity retaining wall in response to the groundwater level fluctuation was derived with Laplace and Fourier transforms. The comparisons with the results from finite element software PLAXIS verified the proposed method. An example was presented to investigate the pore pressure response around the pit and its influence on the stability of the retaining wall via the above semi-analytical solution. The results show that the amplitude of pore pressure attenuated along the seepage path from the back to the front of the retaining wall，while the phase lag increased. The stability of the retaining wall fluctuates and has phase lags too as the groundwater level fluctuating.